Electrically Heated Aerosol Generating System and Method

ABSTRACT

An electrically heated aerosol generating system for receiving an aerosol-forming substrate includes at least one heating element for heating the substrate to form the aerosol and a power supply for supplying power to the at least one heating element. The power supply includes a voltage source, two or more supercapacitors, and switches between the voltage source and the two or more supercapacitors. The switches are arranged so that, during a charging mode, the supercapacitors are connected so as to be charged by the voltage source and, during a heating mode, the supercapacitors are connected so as to discharge through the at least one heating element.

BACKGROUND

The present invention relates to an electrically heated aerosolgenerating system for receiving an aerosol-forming substrate, and amethod for electrically heating an aerosol-forming substrate. Thepresent invention finds particular application as an electrically heatedsmoking system.

A number of prior art documents, for example U.S. Pat. No. 5,060,671,U.S. Pat. No. 5,388,594, U.S. Pat. No. 5,505,214, U.S. Pat. No.5,591,368, WO-A-2004/043175, EP-A-0 358 002, EP-A-0 295 122, EP-A-1 618803, EP-A-1 736 065 and WO-A-2007/131449, disclose electrically operatedsmoking systems, having a number of advantages. One advantage is thatthey significantly reduce sidestream smoke, while permitting the smokerto selectively suspend and reinitiate smoking.

U.S. Pat. No. 5,388,594, the entire contents of which are incorporatedherein by is reference thereto, describes an electrical smoking system.The smoking system includes a cigarette and a reusable lighter. Thecigarette is adapted to be inserted in and removed from an orifice at afront end of the lighter. The lighter includes a housing and has a frontportion and a rear portion. A power source for supplying energy toheating elements for heating the cigarette is disposed in the rearportion of the lighter. The power source is sized to provide sufficientpower for the heating elements that heat the cigarette. The power sourceis preferably replaceable and rechargeable and, in one preferredembodiment, is a battery. The front portion preferably houses heatingelements and circuitry in electrical communication with the powersource. The smoking system is used in much the same fashion as aconventional cigarette.

WO-A-2004/043175 also describes an electrical smoking system. In thatdocument, the electrically heated cigarette smoking device includes anupper heater case cap, a front housing and left and right battery caseportions. A heater unit is positioned below the heater case cap, withthe heater unit fitting inside a partition, which positions the heaterunit relative to the front housing of the device. An opening at the topof the heater case cap allows for the insertion of a cigarette into thetop opening of the heater unit. When the cigarette has been insertedthrough the heater case cap opening and into the heater unit opening, itis positioned in proximity to a plurality of heater blades, arrangedaround the circumference of the cigarette. Slots through the heater casecap provide passageways for ambient air to enter the device when acigarette is positioned in the opening. A printed circuit board ispositioned between the partition and the front housing. A heater unitconnector is positioned below the heater unit within inner housingmembers. This provides electrical connection between the heater bladesand a power source such as a battery, housed within the battery caseportions.

U.S. Pat. No. 5,060,671, the entire contents of which are incorporatedherein by his reference thereto, describes a flavor-generating devicewith a disposable part constituted by the heater and theflavor-generating medium, and a reusable part constituted by the powersource.

Other prior art documents, such as EP-A-0 295 122, EP-A-1 618 803 andEP-A-1 736 065, disclose electrical smoking systems which use a liquidas the aerosol-forming substrate. The liquid may be contained in acartridge which is receivable in a housing. A power supply, such as abattery, is provided, connected to a heater to heat the liquid substrateduring a puff, to form the aerosol which is provided to the smoker.

The electrically heated aerosol generating systems of the prior art,including those described above, typically provide a high power pulse tothe heater to provide a high temperature and to release the volatilecompounds for each puff.

The electrically heated aerosol generating systems of the prior art,including those described above, do have a number of advantages, butthere is still room for improvement in the design. It would beadvantageous if the devices could be made smaller, so that the size iscloser to that of a conventional cigarette and more convenient for theuser.

BRIEF SUMMARY OF SOME ASPECTS OF THE INVENTION

It is therefore an object of the invention to provide an improvedelectrically heated aerosol generating system.

According to a first aspect of the invention there is provided anelectrically heated aerosol generating system for receiving anaerosol-forming substrate, the system comprising: at least one heatingelement for heating the substrate to form the aerosol; and a powersupply for supplying power to the at least one heating element, thepower supply comprising: a voltage source, two or more (i.e., at leasttwo) supercapacitors, and appropriate switches between the voltagesource and the two or more supercapacitors, the switches being arrangedsuch that, during a charging mode, the supercapacitors are connected forcharging by the voltage source and, during a heating mode, thesupercapacitors are connected for discharging through the at least oneheating element.

The invention allows the electrically heated aerosol generating systemto be smaller by using supercapacitors which charge up (i.e., storeelectrical energy) and then discharge (electrical energy) through the atleast one heating element.

In one embodiment, the system further comprises voltage step-up orstep-down circuitry between the voltage source and the two or moresupercapacitors. This is useful if the voltage supplied by the voltagesource does not match the maximum voltage across the two or moresupercapacitors.

Preferably, the power supply is arranged such that, during the chargingmode, the two or more supercapacitors are connected, at least partially,in parallel with each other, and, during the heating mode, the two ormore supercapacitors are connected in series with each other. This isadvantageous because the voltage supplied by the voltage source needriot be the total voltage required across the heating element. This isbecause the supercapacitors are charged in parallel but discharged inseries. In addition, the efficiency of the overall system is increased.

In one embodiment, the system comprises: a portion to be held by a user,and an external charging portion, the portion to be held by a usercomprising the at least one heating element, the two or moresupercapacitors and at least some of the switches required to connectthe two or more supercapacitors during the heating mode, the externalcharging portion comprising the voltage source and at least some of theswitches required to connect the two or more supercapacitors during thecharging mode. This embodiment is advantageous because any circuitryrequired only during charging, and not during heating, can be moved tothe external charging portion. This allows the portion to be h id by auser to be further reduced in size and weight.

The aerosol-forming substrate preferably comprises a tobacco-containingmaterial containing volatile tobacco flavor compounds which are releasedfrom the substrate upon heating. Alternatively, the aerosol-formingsubstrate may comprise a non-tobacco material such as those used in thedevices of EP-A-1 750 788 and EP-A-1 439 876.

Preferably, the aerosol-forming substrate further comprises an aerosolformer, Examples of suitable aerosol formers are glycerine and propyleneglycol. Additional examples of potentially suitable aerosol formers aredescribed in EP-A-0 277 519 and U.S. Pat. No. 5,396,911.

The aerosol-forming substrate may be a solid substrate. The solidsubstrate may comprise, for example, one or more of: powder, granules,pellets, shreds, spaghettis, strips or sheets containing one or more of:herb leaf, tobacco leaf, fragments of tobacco ribs, reconstitutedtobacco, homogenized tobacco, extruded tobacco and expanded tobacco. Thesolid substrate may be in loose form, or may be provided in a suitablecontainer or cartridge. Optionally, the solid substrate may containadditional tobacco or non-tobacco volatile flavor compounds, to bereleased upon heating of the substrate.

Optionally, the solid substrate may be provided on or embedded in athermally stable carrier. The carrier may take the form of powder,granules, pellets, shreds, spaghettis, strips or sheets. Alternatively,the carrier may be a tubular carrier having a thin layer of the solidsubstrate deposited on its inner surface, such as those disclosed inU.S. Pat. No. 5,505,214, U.S. Pat. No. 5,591,368, and U.S. Pat. No.5,388,594, the entire co tents of each patent are incorporated herein bythis reference thereto, or on its outer surface, or on both its innerand outer surfaces. Such a tubular carrier may be formed of, forexample, a paper, or paper like material, a non-woven carbon fiber mat,a low mass open mesh metallic screen, or a perforated metallic foil orany other thermally stable polymer matrix.

The solid substrate may be deposited on the surface of the carrier inthe form of, for example, a sheet, foam, gel or slurry. The solidsubstrate may he deposited on the entire surface of the carrier, oralternatively, may be deposited in a pattern in order to provide anon-uniform flavor delivery during use.

Alternatively, the carrier may be a non-woven fabric or fiber bundleinto which tobacco components have been incorporated, such as thatdescribed in EP-A-0 857 431. The non-woven fabric or fiber bundle maycomprise, for example, carbon fibers, natural cellulose fibers, orcellulose derivative fibers.

Alternatively, the carrier may be at least a part of the heating elementof the electrically heated aerosol generating system. In such cases, theheating element is typically disposable. For example, the solidsubstrate may be deposited as a thin layer on a metallic foil or on anelectrically resistive support as described in U.S. Pat. No. 5,060,671.

The aerosol-forming substrate may alternatively be a liquid substrate.If a liquid substrate is provided, the electrically heated aerosolgenerating system preferably comprises means for retaining the liquid.For example, the liquid substrate may be retained in a container, suchas that described in EP-A-0 893 071. Alternatively or in addition, theliquid substrate may be absorbed into a porous carrier material, asdescribed in WO-A-2007/024130, WO-A-2007/066374, EP-A-1 736 062,WO-A-2007/131449 and WO-A-2007/131450. The porous carrier material maybe made from any suitable absorbent plug or body, for example, a foamedmetal or plastics material, polypropylene, terylene, nylon fibers orceramic. The liquid substrate may be retained in the porous carriermaterial prior to use of the electrically heated aerosol generatingsystem or alternatively, the liquid substrate material may be releasedinto the porous carrier material during, or immediately prior to use.For example, the liquid substrate may be provided in a capsule, asdescribed in WO-A-2007/077167. The shell of the capsule preferably meltsupon heating and releases the liquid substrate into the porous carriermaterial. The capsule may optionally contain a solid in combination withthe liquid.

If the aerosol-forming substrate is a liquid substrate, the electricallyheated aerosol generating system may further comprise means for heatinga small amount of liquid at a time. The means for heating a small amountof liquid at a time may include, for example, a liquid passageway incommunication with the liquid substrate, as described in EP-A-0 893 071.The liquid substrate is typically forced into the liquid passageway bycapillary force. The heating element is preferably arranged such thatduring use, only the small amount of liquid substrate within the liquidpassageway, and not the liquid within the container, is heated andvolatilised.

Alternatively, or in addition, if the aerosol-forming substrate is aliquid substrate, the electrically heated aerosol generating system mayfurther comprise an atomizer in contact with the liquid substrate sourceand including the at least one heating element. In addition to theheating element, the atomizer may include one or more electromechanicalelements such as piezoelectric elements. Additionally or alternatively,the atomizer may also include elements that use electrostatic,electromagnetic or pneumatic effects. The electrically heated aerosolgenerating system may still further comprise a condensation chamber.

The aerosol-forming substrate may alternatively be any other sort ofsubstrate, for example, a gas substrate, or any combination of thevarious types of substrate. During operation, the substrate may becompletely contained within the electrically heated aerosol generatingsystem. In that case, a user may puff on a mouthpiece of theelectrically heated aerosol generating system. Alternatively, duringoperation, the substrate may be partially contained within theelectrically heated aerosol generating system. In that case, thesubstrate may form part of a separate article and the user may puffdirectly on the separate article.

The at least one heating element may comprise a single heating element.Alternatively, the at least one heating element may comprise more thanone heating element. The heating element or heating elements may bearranged appropriately on as to most effectively heat theaerosol-forming substrate.

The at least one heating element preferably comprises an electricallyresistive material. Suitable electrically resistive materials includebut are not limited to: semiconductors such as doped ceramics,electrically “conductive” ceramics (such as, for example, molybdenumdisilicide), carbon, graphite, metals, metal alloys and compositematerials made of a ceramic material and a metallic material, Suchcomposite materials may comprise doped or undoped ceramics. Examples ofsuitable doped ceramics include doped silicon carbides. Examples ofsuitable metals include titanium, zirconium, tantalum and metals fromthe platinum group Examples of suitable metal alloys include stainlesssteel, nickel-, cobalt-, chromium-, aluminium- titanium- zirconium-,hafnium-, niobium-, molybdenum-, tantalum-, tungsten-, tin-, gallium-,manganese- and iron-containing alloys, and super-alloys based on nickel,iron, cobalt, stainless steel. Timetal® and iron-manganese-aluminiumbased alloys. In composite materials, the electrically resistivematerial may optionally be embedded in, encapsulated or coated with aninsulating material or vice-versa, depending on the kinetics of energytransfer and the external physicochemical properties required. Examplesof suitable composite heating elements are disclosed in U.S. Pat. No.5,498,855, the entire contents of which are incorporated herein by thisreference thereto, WO-A-03/095688 and U.S. Pat. No. 5,514,630.

Alternatively, the at least one heating element may comprise aninfra-red heating element, a photonic source such as, for example, thosedescribed in U.S. Pat. No. 5,934,289, the entire contents of which areincorporated herein by this reference thereto, or an inductive heatingelement, such as, for example, those described in U.S. Pat. No.5,613,505, the entire contents of which are incorporated herein by thisreference thereto.

The at least one heating element may take any suitable form. Forexample, the at least one heating element may take the form of heatingblade, such as those described in U.S. Pat. No. 5,388,594, U.S. Pat. No.5,591,368, the entire contents of which are incorporated herein by thisreference thereto, and U.S. Pat. No. 5,505,214, the entire contents ofwhich are incorporated herein by this reference thereto. Alternatively,the at least one heating element may take the form of a casing orsubstrate having different electro-conductive portions, as described inEP-A-1 128 741, or an electrically resistive metallic tube, as describedin WO-A-2007/066374. Where the aerosol-forming substrate is a liquidprovided within a container, the container may incorporate a disposableheating element. Alternatively, one or more heating needles or rods thatrun through the centre of the aerosol-forming substrate, as described inKR-A-100636287 and JP-A-2006320286, may also be suitable. Alternatively,the at least one heating element may be a disk (end) heater or acombination of a disk heater with heating needles or rods. Otheralternatives include a heating wire or filament, for example a Ni—Cr,platinum, tungsten or alloy wire, such as those described in EP-A-1 736065, or a heating plate. Optionally, the heating element may bedeposited in or on a rigid carrier material.

The at least one heating element may comprise a heat sink, or heatreservoir comprising a material capable of absorbing and storing heatand subsequently releasing the heat over time to the aerosol-formingsubstrate. Suitable heat sinks are described in EP-A-0 857 431, U.S.Patent Application Publication 2006/118128, and WO-A-2008/015441. Theheat sink may be formed of any suitable material, such as a suitablemetal or ceramic material. Preferably, the material has a high heatcapacity (sensible heat storage material), or is a material capable ofabsorbing and subsequently releasing heat via a reversible process, suchas a high temperature phase change. Suitable sensible heat storagematerials include silica gel, alumina, carbon, glass mat, glass fiber,minerals, a metal or alloy such as aluminium, silver or lead, and acellulose material such as paper. Other suitable materials which releaseheat via a reversible phase change include paraffin, sodium acetate,naphthalene, wax, polyethylene oxide, a metal, metal salt, a mixture ofeutectic salts or an alloy.

The heat sink or heat reservoir may be arranged such that it is directlyin contact with the aerosol-forming substrate and can transfer thestored heat directly to the substrate, as described in EP-A-0 857 431.Alternatively, the heat stored in the heat sink or heat reservoir may betransferred to the aerosol-forming substrate by means of a heatconductor, such as a metallic tube, as described in WO-A-2008/015441.

The at least one heating element may heat the aerosol-forming substrateby means of conduction. The heating element may be at least partially incontact with the substrate, or the carrier on which the substrate isdeposited. Alternatively, the heat from the heating element may beconducted to the substrate by means of a heat conductive element.

Alternatively, the at least one heating element may transfer heat to theincoming ambient air that is drawn through the electrically heatedaerosol generating system during use, which in turn heats theaerosol-forming substrate by convection. The ambient air may be heatedbefore passing through the aerosol-forming substrate, as described inWO-A-2007/066374. Alternatively, if the aerosol-forming substrate is aliquid substrate, the ambient air may be first drawn through thesubstrate and then heated, as described in WO-A-2007/078273.

Preferably, the two or more supercapacitors of the power supply arearranged into two or more groups of supercapacitors, each groupcomprising one supercapacitor or two or more supercapacitors in series.Preferably during the charging mode, the two or more groups ofsupercapacitors are connected in parallel with each other and, duringthe heating mode, the two or more groups of supercapacitors areconnected in series with each other. The two or more supercapacitors maycomprise two, three, four, five, six or more supercapacitors, or anyother appropriate number of supercapacitors. The two or more groups ofsupercapacitors may comprise two, three, four, five, six or more groups,or any other appropriate number of groups. The appropriate number ofsupercapacitors may be used in each group, according to the voltagerequired.

In one embodiment, the system further comprises a sensor to detect airflow indicative of a user taking a puff. The sensor may be anelectro-mechanical device. Alternatively, the sensor may be any of: amechanical device, an optical device, an opto-mechanical device and amicro electro mechanical systems (MEMS) based sensor. In thatembodiment, preferably, the sensor is connected to the power supply andthe system is arranged to switch the switches into the heating mode,when the sensor senses a user taking a puff. When a puff is detected, ahigh energy pulse is required at the heating element. Thesupercapacitors will discharge through the heating element at that time,thereby creating the required high current pulse.

In an alternative embodiment, the system further comprises a manuallyoperable switch, for a user to initiate a puff.

Preferably, one or more of the switches are solid-state switches.Preferably, the one or more solid-state switch is a MOSFET(metal-oxide-semiconductor-field-effect-transistor) switch.Alternatively, the one or more solid-state switch may be any other typeof FET (field-effect-transistor) switch. Particularly advantageous arethose switches having very low resistance when closed, when comparedwith the resistance of the heating element.

Preferably, the system further comprises a housing for receiving theaerosol-forming substrate and designed to be grasped by a user.

In one preferred embodiment, the voltage source is a DC voltage source.In one embodiment, the voltage source is a lithium-ion battery.Alternatively, the voltage source may be a nickel-metal-hydride batteryor a nickel-cadmium battery. In one preferred embodiment, the two ormore supercapacitors are electrochemical double layer supercapacitors.In another preferred embodiment, the two or more supercapacitors aresupercapacitors comprising nanoporous material. In an alternativeembodiment, the two or more supercapacitors may include a combination ofelectrochemical double layer supercapacitors and supercapacitorscomprising nanoporous material.

Features described in relation to the system of U.S. Pat. No. 5,388,594or the system of WO-A-2004/043175 may be incorporated into the system ofthe invention.

According to a second aspect of the invention, there is provided amethod of electrically heating an aerosol-forming substrate, the methodcomprising the Steps of: providing at least one heating element forheating the substrate to form the aerosol; providing a power supply forsupplying power to the at least one heating element, the power supplycomprising a voltage source, two or more supercapacitors, and switchesbetween the voltage source and the two or more supercapacitors; during acharging mode, switching the switches so that the two or moresupercapacitors are connected for charging by the voltage source; andduring a heating mode, switching the switches so that thesupercapacitors are connected for discharging through the at least oneheating element.

Preferably, the two or more supercapacitors are arranged into two ormore groups of supercapacitors, each group comprising one supercapacitoror two or more supercapacitors in series. Preferably during the chargingmode, the two or more groups of supercapacitors are connected inparallel with each other and, during the heating mode, the two or moregroups of supercapacitors are connected in series with each other. Theappropriate number of supercapacitors may be used in each group,according to the voltage required.

Preferably, one or more of the switches are solid-state switches.Preferably, the or each solid-state switch is a MOSFET(metal-oxide-semiconductor-field-effect-transistor) switch.

Features described in relation to one aspect of the invention may alsobe applicable to another aspect of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be further described, by way of example only, withreference to the accompanying drawings wherein like reference numeralsare applied to like elements and wherein:

FIG. 1 is a schematic of a first embodiment of a power supply for anelectrically heated aerosol generating system;

FIG. 2 is a schematic of a second embodiment of a power supply for anelectrically heated aerosol generating system;

FIG. 3 is a schematic of a third embodiment of a power supply for anelectrically heated aerosol generating system; and

FIG. 4 is a schematic of a fourth embodiment of a power supply for anelectrically heated aerosol generating system.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

As already mentioned, known electrical smoking systems typically usebattery packs as the power source. They power both the controlelectronics and the heater for heating the substrate. In the electricalsmoking system described in WO-A-2004/043175, three lithium-ion (Li-ion)cells (approximately 3.7 V each) may be connected in series to providean 11.1 V battery supply. This high voltage is required in order toprovide the necessary power to the heater, particularly for the highpower pulse required for each puff.

Although Li-ion cells do have a high energy density, they are notparticularly efficient in high power applications, such as electricallyheated aerosol generating systems, in which high current dissipation isneeded in short bursts. The internal resistance of the three cellscauses a significant voltage drop with high current loads. In addition,because the three cells are in series, some additional electroniccircuitry is required, in order to ensure that the cells do not exceedthe maximum rated voltage. In addition, the three Li-ion cells requiredmeans the electrically heated aerosol generating system may be largerthan desired.

As already described, the invention provides a new power supply for anelectrically heated aerosol generating system, which makes use ofsupercapacitors. Supercapacitors may also be referred to asultracapacitors.

Supercapacitors are a particular type of capacitor having a largecapacity in a small volume. They have an unusually high energy densitywhen compared with standard capacitors. The most common type ofsupercapacitor is an electrochemical double layer supercapacitor(referred to as an “EDL supercapacitor”). Instead of using a dielectricas such, an EDL supercapacitor comprises a double layer of conductingmaterial, with the two layers in contact. Although each layer isconducting, the interface between the two layers is insulating. Such anEDL supercapacitor typically provides approximately 2.5 V per cell.However, EDL supercapacitors do tend to have a relatively high inter alresistance. On the other hand, a supercapacitor using a nanoporousmaterial instead of the conventional insulating barrier (referred to asa “nanoporous supercapacitor”), for example those made by NanotectureLimited, may have a voltage of approximately 14 V per cell, but have thepotential for a small internal resistance. Supercapacitors have the samedischarge characteristics as standard capacitors. However, nanoporoussupercapacitors tend to maintain the voltage during much of thedischarge phase.

FIG. 1 shows a first embodiment of a power supply 101 for anelectrically heated aerosol generating system. The supply 101 includes asingle Li-ion cell 103 providing a voltage of 3.7 V and a group of fourEDL supercapacitors 105 (each 2.5 V) in series, forming a stack. Becausethe voltage across the supercapacitors 105 (10 V in total), is higherthan the voltage across the cell 103, voltage step-up circuitry 107 isalso required. Also shown in FIG. 1, although not actually part of thepower supply itself, is resistor 109 which forms the heating element forheating the substrate. In this embodiment, four EDL supercapacitors of2.5 V each are used in the stack. However, these could be replaced byseven or eight nanoporous supercapacitors of 1.4 V each.

During charging, a first switch S1 is closed and the supercapacitors 105are charged. After charging, first S1 may be opened. When the high powerpulse is required for the puff, a second switch S2 is closed and firstswitch S1 remains open. Then, the supercapacitors discharge through theresistor 109, thereby providing the required high current throughresistor 109. If a series of high power pulses is required, secondswitch S2 may be repeatedly closed and opened, allowing a partialdischarge for each pulse.

In FIG. 1, first and second switches S1, S2 are under control of a puffdetection and control system 111. First switch S1 (for charging thesupercapacitors controlled by capacitor charge controller 113, andsecond switch S2 (for discharging the supercapacitors through theresistor) is controlled by energy delivery protocol 115. A third switchS3 is a switch used to initiate a puff. This switch may be a sensor, forsensing a puff, or a manually operable switch.

One of the advantages of the FIG. 1 arrangement is that only a singleLi-ion cell 103 is required. This allows the electrically heated aerosolgenerating system to be considerably reduced in size. However, in thevoltage step-up circuitry 107, a large inductor coil is required tomatch the high current loading needed during charging of thesupercapacitors. This compensates for any decrease in size due to therebeing only one Li-ion cell. In addition, the efficiency of the voltagestep-up circuitry is unlikely to be more than 80%.

FIG. 2 shows a second embodiment of a power supply for an electricallyheated aerosol generating system. The power supply 201 includescircuitry 203 incorporated into a portion to be held by a user, plus anexternal DC voltage source 205. The circuitry 203 and voltage source 205are connected via connectors 207 and 209. In this embodiment, thevoltage source 205 provides a voltage of 5V. The circuitry includes agroup of two EDL supercapacitors 211 (each 2.5 V) in series (up to 5 Vtotal), forming a stack, and first and second switches S1, S2. Alsoshown in FIG. 2, although not actually part of the power supply itself,is resistor 213, which forms the heating element. Just as in FIG. 1first and second switches S1, S2 are under control of a puff detectionand control system 215. First switch S1 (for charging thesupercapacitors) is controlled by capacitor charge controller 217, andsecond switch S2 (for discharging the supercapacitors through theresistor) is controlled by energy delivery protocol 219. The thirdswitch S3 is used to initiate a puff and may be a sensor or a manuallyoperable switch.

During charging, connectors 207 and 209 are in electrical contact, firstswitch S1 is closed and the supercapacitors 211 are charged. When a puffis required, connectors 207 and 209 are disconnected. When a user drawsa puff, second switch S2 is closed and first switch S1 is opened. Then,the supercapacitors discharge through the heating element.

In FIG. 2, no voltage step-up circuitry 107 is required. This is becausethe voltage of the supercapacitors matches that of the DC voltage source205. One of the advantages of the FIG. 2 arrangement is that the size ofthe electrically heated aerosol generating system can be reduced becauseneither a plurality of cells nor voltage step-up circuitry is required.Although FIG. 2 shows circuitry 203 and an external voltage source 205,it is possible for the voltage source to be incorporated into theportion to be held by the user.

FIG. 3 shows a third embodiment of a power supply for an electricallyheated aerosol generating system. The power supply 301 includes a DCvoltage source in the form of a single Li-ion cell 303 providing avoltage of 3.7 V, and two or more supercapacitors formed into a firstgroup of three nanoporous supercapacitors 305 in series (up to 4.2 V intotal), forming a first stack, arid a second group of three nanoporoussupercapacitors 307 in series (also up to 4.2 V in total), forming asecond stack. The circuitry also includes a plurality of switches S1 toS5. Also shown in FIG. 3, although not actually part of the power supplyitself, is a resistor 309 which forms the heating element for heatingthe substrate. In this embodiment, three nanoporous supercapacitors of1.4 V each are used in each stack. However, these could be replaced bytwo EDL supercapacitors of 2.5 V each. In FIG. 3, switches S1 to S5 areunder control of digital controller 311. Switch S6 is a switch used toinitiate a puff, and may be a sensor or a manually operable switch.

During charging, switches S4 and S5 are open and switches S1, S2 and S3are closed. The two supercapacitor stacks 305 and 307 are therefore inparallel. After charging, S1 and S2 may be opened. When the high powerpulse is required for the puff, switch S3 is opened and switches S4 andS5 are closed, while switches S1 and S2 remain open. Then, thesupercapacitor stacks 305 and 307 are in series, so discharge in seriesthrough the resistor 309, thereby providing the required high currentthrough resistor 309. If a series of high power pulses is required,switch S5 may be repeatedly closed and opened, allowing a partialdischarge for each pulse. The supercapacitors may be re-charged betweenpuffs. Alternatively, the supercapacitors may be only partiallydischarged during each pulse, so that a number of puffs can be takenbefore re-charge is required.

Because the capacitor stacks 305 and 307 are charged in parallel eachcapacitor stack only needs to be charged to around the same voltage asthat of the Li-ion cell 303 i.e. approximately 3.7 V. However, when thestacks are connected in series for discharging, the voltage across thetwo stacks is twice that of the Li-ion cell i.e. approximately 7.4 V.So, the required high voltage can be provided for the high power pulse,without the need for voltage step-up circuitry. Each stack could hecharged to less than the total cell voltage, if required, and theswitches S1 and S2 used to stop the charging at the required voltage. Ofcourse, further stacks could be provided if required, or individualsupercapacitors, instead of stacks, could be used if suitable.

In the embodiment illustrated in FIG. 3, all the switches S1 to S5 areMOSFET switches. This type of switch, and indeed other solid-stateswitches, is advantageous since they have a negligible resistance whenclosed.

FIG. 4 shows a fourth embodiment of a power supply for an electricallyheated aerosol generating system, in which power supply 401 comprisescircuitry 403 incorporated into a portion to be held by a user andexternal charger 405. The circuitry 403 comprises a connector 407 forconnection to charger 405, two or more supercapacitors formed into afirst group Of three nanoporous supercapacitors 409 in series (up to 4.2V in total), forming a first stack, and a second group of threenanoporous supercapacitors 411 in series also up to 4.2 V in total)forming a second stack. Circuitry 403 also includes switches S4 and S5,both of which are controlled by digital controller 413. Switch S6 is aswitch used to initiate a puff, and may be a sensor or a manuallyoperable switch. Also shown in FIG. 4, although not actually part of thepower supply itself, is a resistor 421 which forms the heating elementfor heating the substrate. The charger 405 comprises a connector 415 forconnection to circuitry 403, a charge controller 417, a voltage supply419 (in this case, 5 V) and switches S1, S2 and S3, under the control ofthe charge controller 417. The charger 405 also includes a lightemitting diode D1, which is switched on when the charger is operating.

Between puffs, the electrically heated aerosol generating system can becharged. So, the system can be connected to a charger and connectors 407and 415 are then in electrical contact. During that time, switches S1,S2 and S3 are closed and the supercapacitors 409 and 411 are charged inparallel. When a puff is required, the electrically heated aerosolgenerating system is removed from the charger, so that connectors 407and 415 e disconnected. When the user draws air through the system, orat another prompt, controller 413 closes switches S4 and S5, allowingthe supercapacitors 409 and 411 to discharge in series through heatingelement 421.

Thus, the arrangement of FIG. 4 makes use of the supercapacitorarrangement of FIG. 3, but allows the system to be reduced even furtherin size by moving much of the necessary circuitry into the externalcharger.

The invention could, of course, be used for different voltages simply byvarying one or more of: the total number of supercapacitors used, thearrangement of the supercapacitors (either individual or in stacks); thetype of supercapacitors; and the supply voltage. In addition, theswitches S1 and S2 could be used for voltage monitoring to ensure thatthe charge voltage does not exceed the maximum rating of the individualsupercapacitors. S1 and S2 could also be used to charge the stacks to alower voltage than the supply voltage.

As described, the invention provides an efficient power supply for anelectrically heated aerosol generating system. Supercapacitors provide anumber of advantages over batteries, such as their low internalresistance, their high efficiency, their high output power and their lowheating levels and consequent safety.

1. An electrically heated aerosol generating system for receiving anaerosol-forming substrate, the system comprising: at least one heatingelement for heating the substrate to form the aerosol; and a powersupply for supplying power to the at least one heating element, thepower supply comprising: a voltage source, at least two supercapacitors,switches between the voltage source and the at least twosupercapacitors, the switches being arranged such that, during acharging mode, the supercapacitors are connected for charging by thevoltage source and, during a heating mode, the supercapacitors areconnected for discharging through the at least one heating element; andvoltage step-up or step-down circuitry between the voltage source andthe at least two supercapacitors.
 2. (canceled)
 3. The electricallyheated aerosol generating system according to claim 1, wherein the powersupply is arranged such that, during the charging mode, the at least twosupercapacitors are connected, at least partially, in parallel with eachother, and during the heating mode, the at least two supercapacitors areconnected in series with each other.
 4. The electrically heated aerosolgenerating system according to claim 1, wherein the system furthercomprises: a hand held portion to be held by a user, and an externalcharging portion, the hand held portion to be held by a user comprisingthe at least one heating element, the at least two supercapacitors andat least some of the switches required to connect the at least twosupercapacitors during the heating mode, the external charging portioncomprising the voltage source and at least some of the switches requiredto connect the at least two supercapacitors during the charging mode. 5.The electrically heated aerosol generating system according to claim 1,including a solid aerosol-forming substrate.
 6. The electrically heatedaerosol generating system according to claim 1, including a liquidaerosol-forming substrate.
 7. The electrically heated aerosol generatingsystem according to claim 1, wherein the at least two supercapacitorsare arranged into two groups of supercapacitors, each group comprisingone supercapacitor or at least two supercapacitors in series, andwherein, during the charging mode, the at least two groups are connectedin parallel with each other, and during the heating mode, the at leasttwo groups are connected in series with each other.
 8. The electricallyheated aerosol generating system according to claim 1, further includinga sensor to detect air flow in response to a user taking a puff.
 9. Theelectrically heated aerosol generating system according to claim 1,wherein at least one of the switches is a solid state switch.
 10. Amethod of using the electrically heated aerosol generating system ofclaim 4, the method comprising the steps of: during a charging mode,selectively operating the switches so that the at least twosupercapacitors are connected in parallel for charging by the voltagesource; and during a heating mode, selectively operating the switches sothat the at least two supercapacitors are connected in series fordischarging through the at least one heating element.
 11. Theelectrically heated aerosol generating system according to claim 4,wherein the external charging portion includes a controller that isconfigured to change a position of the first switches during the heatingand charging modes.
 12. The electrically heated aerosol generatingsystem according to claim 4, wherein the controller is configured toclose the first switches when, during the charging mode, the hand heldportion is connected to the external charging portion.
 13. Theelectrically heated aerosol generating system according to claim 4,wherein the controller is configured to open the first switches when,during the heating mode, the hand held portion is disconnected from theexternal charging portion.
 14. The method according to claim 10, whereinthe external charging portion includes a controller that is configuredto change a position of the first switches during the heating andcharging modes.
 15. The method according to claim 10, wherein thecontroller is configured to close the first switches when, during thecharging mode, the hand held portion is connected to the externalcharging portion.
 16. The method of claim 10, wherein the controller isconfigured to open the first switches when, during the heating mode, thehand held portion is disconnected from the external charging portion.